Your ex skill is free on Shingen so you can still run SS.
Yep. and it seems like she always starts at 80% even MLB, meaning that you're loosing from 4% to 8% light atk for each non-light eidolon.
Edit : just to be precise , it only concern sub eidolons. You can still run Thunderbird or Behemoth as main/ support
No offense but i'm a bit skeptical about those build. I would agree with Arthur and Morgan, with Triya instead of Eros